Currently known polyester based hot-melt adhesives are all prepared by further subjecting the products of transesterification of dibasic esters with diols, or the products of esterification of dibasic acids with diols, to a low-pressure polycondensation. For example, U.S. Pat. No. 6,255,443 discloses a method for preparation of low-melting copolyester hot-melt adhesives. Chinese Publication No. CN 1340585 provides a process for preparing a high-melting copolyester hot-melt adhesive. Moreover, Chinese Application No. 200710043238.2 describes an improved copolyester hot-melt adhesive obtained by modifying the copolyester with a metal salt of sorbic acid and an ethylene/acrylic acid copolymer.
Although, in the preparation of all these copolyester hot-melt adhesives, non-linear molecular materials, such as isophthalic acid, are added to impede them from having a linear molecular structure, so as to satisfy certain demands of garment and other industries, due to their slow crystallizing and solidifying properties, when used in the processing of interlinings, they will cause a so-called “stick-back” problem. Therefore, the conventional hot-melt adhesives are neither suitable for production-line applications where fast adhesion is required, nor can be used to produce films or double-sided adhesive nets.
In contrast, the present invention provides a method for the preparation of a polyester/glyoxalated polyvinyl alcohol semi-interpenetrating polymer network hot-melt adhesive, which has incomparable advantages in performance over those produced by other polymerization techniques. This hot-melt adhesive is characterized in maintaining a potential reactivity under normal production conditions, while having the capability of forming, at a relatively low temperature, an internal interpenetrating network which will reduce or eliminate its thermo-plasticity and impart it improved wash and solvent resistance. In particular, compared to the conventional non-crosslinked products, the hot-melt adhesive in accordance with the invention has both a lower melting point and a higher crystallization rate, which enables it to be used with high performance in widespread applications, such as garment production lines, customized production of various films or adhesive nets, and long-term, high-temperature applications.